From 3f9de66f8acbf8ff45a91b4920605ed10c6b7c06 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 12 Jun 2026 20:36:48 +0300 Subject: [PATCH] drm/i915/cdclk: Fix up CDCLK_FREQ_DECIMAL without a full PLL re-enable MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The GOP (and even Bspec on some platforms) is a bit inconsistent on what the CDCLK_FREQ_DECIMAL divider should be. Currently any mismatch there causes a full CDCLK PLL disable+re-enable, which we really don't want to do if any displays are currently active. Let's instead just reprogram CDCLK_FREQ_DECIMAL when that is the only thing amiss. For any other (more serious) mismatch we still punt to the full PLL reprogramming. We also need to tweak the bxt_cdclk_cd2x_pipe() stuff a bit to consistently select pipe==NONE since we have no idea which pipes are enabled at this point. Since we're not actually changing the CDCLK frequency here we don't need to sync the update to any pipe. Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16209 Signed-off-by: Ville Syrjälä Link: https://patch.msgid.link/20260612173653.7830-2-ville.syrjala@linux.intel.com Reviewed-by: Michał Grzelak --- drivers/gpu/drm/i915/display/intel_cdclk.c | 41 ++++++++++++++++++---- 1 file changed, 34 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c index 189ae2d3cfc9..7bc9b956554b 100644 --- a/drivers/gpu/drm/i915/display/intel_cdclk.c +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c @@ -1256,9 +1256,22 @@ static void skl_sanitize_cdclk(struct intel_display *display) cdctl = intel_de_read(display, CDCLK_CTL); expected = (cdctl & CDCLK_FREQ_SEL_MASK) | skl_cdclk_decimal(display->cdclk.hw.cdclk); - if (cdctl == expected) - /* All well; nothing to sanitize */ - return; + + if (cdctl != expected) { + cdctl &= ~CDCLK_FREQ_DECIMAL_MASK; + cdctl |= expected & CDCLK_FREQ_DECIMAL_MASK; + + if (cdctl != expected) + goto sanitize; + + drm_dbg_kms(display->drm, "Sanitizing CDCLK decimal divider (CDCLK_CTL 0x%x, expected 0x%x)\n", + intel_de_read(display, CDCLK_CTL), expected); + + intel_de_write(display, CDCLK_CTL, expected); + } + + /* All well; nothing to sanitize */ + return; sanitize: drm_dbg_kms(display->drm, "Sanitizing cdclk programmed by pre-os\n"); @@ -2354,11 +2367,25 @@ static void bxt_sanitize_cdclk(struct intel_display *display) * (PIPE_NONE). */ cdctl &= ~bxt_cdclk_cd2x_pipe(display, INVALID_PIPE); - expected &= ~bxt_cdclk_cd2x_pipe(display, INVALID_PIPE); + cdctl |= bxt_cdclk_cd2x_pipe(display, INVALID_PIPE); - if (cdctl == expected) - /* All well; nothing to sanitize */ - return; + if (cdctl != expected) { + if (DISPLAY_VER(display) < 20) { + cdctl &= ~CDCLK_FREQ_DECIMAL_MASK; + cdctl |= expected & CDCLK_FREQ_DECIMAL_MASK; + } + + if (cdctl != expected) + goto sanitize; + + drm_dbg_kms(display->drm, "Sanitizing CDCLK decimal divider (CDCLK_CTL 0x%x, expected 0x%x)\n", + intel_de_read(display, CDCLK_CTL), expected); + + intel_de_write(display, CDCLK_CTL, expected); + } + + /* All well; nothing to sanitize */ + return; sanitize: drm_dbg_kms(display->drm, "Sanitizing cdclk programmed by pre-os\n");